Millimeter-wave (MMW) devices are valued for their ability to provide very-broad-bandwidth wireless communication in both space and terrestrial applications. Examples include satellite, radar, mobile collision detection, imaging, and indoor local communications. One aspect of wireless millimeter-wave systems is their radiating structures, i.e., the antenna. Planar MMW antennas, such as microstrip antennas or printed-circuit patch antennas, are widely used due to their ease of manufacture, low cost, simple fabrication, and relative ease of integration with monolithic systems. However, patch antennas can suffer from relatively narrow bandwidth, substrate dielectric loss, mutual coupling with their substrate, and surface wave perturbation issues. Although wire antennas (i.e., dipole or monopole antennas) or cavity antennas can be considered as alternatives to printed-circuit patch antennas due to their broad bandwidth, low loss, and reduced dependence on substrate, fabrication difficulty has prevented them from being efficiently implemented in a cost effective, integrated fashion.
Increases in operation frequencies of RF systems have pushed characteristic sizes of RF sub-elements small enough, but advances in fabrication technologies have, to date, not been such that surface micro-machine components have been sufficiently large to create reliable radiators in the desired millimeter-wave frequency range. FIG. 1 is a nonlimiting exemplary diagram of a plate molding process for fabricating a monopole antenna. In this nonlimiting example 10, a mold 12 having a hole 13 may be placed on substrate 15, such that a conductor material may be deposited in hole 13 to create the monopole column 17 of FIG. 1. In order to produce the monopole column 17, the mold 12 is removed so as to leave the remaining column 17 vertically extending from substrate 15.
However, fabrication techniques such as described above to produce monopole antenna column 17 are difficult and costly due to the problems associated with removing the mold 12 without damaging or perhaps destroying the monopole antenna 17. Because of these difficulties and cost issues, the achievable thicknesses and vertical heights of monopole antenna 17 have been limited, thereby precluding the available frequencies precluding application in certain millimeter-wave frequencies.
However, with a growing demand for higher data rate and affordable communication modules, increasing bandwidth and reduced fabrication costs have come into sharper focus, especially in the millimeter frequency range. Moreover, use of cylindrical monopole antennas such as monopole antenna 17 of FIG. 1 are desired in such applications due to their broad impedance bandwidths. But, as described above in regard to FIG. 1, one problem in addition to column height relates to difficulties in transitioning from 2-D components to 3-D components. It is generally more complicated to create a 3-D transition from the planar transmission systems that may be placed on substrate 15 as coupled to the monopole antenna 17 than for printed circuit antennas. As a nonlimiting example, for lower frequency systems, a cylindrical monopole antenna, such as monopole antenna 17 of FIG. 1, may be fed from the backside of substrate 15 by a coaxial line (not shown); however, this fabrication technique includes an etching process that may be overly costly.
Thus, there is a heretofore unaddressed need to overcome these deficiencies and shortcomings described above.